Guides

How to Charge Late Fees on an Invoice (Wording and Email Templates)

A late fee gives clients a reason to pay on time and compensates you when they don't. But a fee that shows up out of nowhere usually starts an argument instead of a payment. The fee that works is one the client agreed to before the work began, written clearly on every invoice and applied calmly when it's due. Here's how to set one up, the wording to use, and emails for when you actually charge it.

Step 1: Put the late fee in your agreement first

The invoice should remind the client of a term they already accepted, not introduce a new one. Add the late fee to your contract, proposal or statement of work before the project starts. If you have no written agreement and the fee wasn't mentioned up front, it's generally hard to enforce, so start with your next client or your next project with this one.

Subject: Late payment clause for your contract

Payment terms: Invoices are due within [30] days of the invoice date.

Late payment: If an invoice remains unpaid [7] days after its due date, a late fee of [1.5% per month on the unpaid balance / a one-time fee of $[amount]] will apply, calculated from the original due date until paid in full, or the maximum rate permitted by law if lower.

Step 2: Choose the type of fee

• Flat fee: a one-time charge, such as a set dollar amount, once the invoice is a certain number of days late. Simple to explain and calculate.
• Percentage of the balance: a one-time charge of a small percentage of what's unpaid. Scales with the invoice size.
• Monthly interest: a percentage of the unpaid balance added each month it stays unpaid. Keeps pressure on long-overdue invoices.
• A grace period: a few days after the due date before any fee applies. It keeps goodwill with clients who are only slightly late.

Whatever you choose, keep it reasonable. Many places limit how much interest or how large a fee you can charge, and rules differ by state and country, so check what applies to you. Describe it as a late fee or finance charge rather than a penalty.

Step 3: Add clear wording to every invoice

Good invoice wording says four things: the amount or rate, when it starts, what it applies to, and where the client agreed to it. Put it in the payment terms area near the due date.

• Flat fee: "Payment due [date]. A one-time late fee of $[amount] applies to any balance unpaid [7] days after the due date, per our agreement dated [date]."
• Monthly interest: "Balances unpaid after [date] accrue [1.5]% per month on the unpaid amount, per clause [number] of our agreement."
• Grace period: "Payment due [date]. No fee if received by [date + 7 days]. After that, a late fee of [rate] applies per our agreement."

Step 4: Calculate the fee correctly

For a monthly rate, multiply the unpaid balance by the rate for each month it's overdue. For example, an unpaid balance of $1,000 at 1.5% per month adds $15 for one month. If your agreement states an annual rate, divide it by 12 to get the monthly rate. Apply the rate to the unpaid amount only, not to fees already added. ChaseOwl's free late fee calculator on chaseowl.com/tools does this math for you.

Step 5: Tell the client before you apply it

A short warning a few days before the fee kicks in often gets the invoice paid without charging anything at all, which is usually the outcome you want.

Subject: Invoice #[number]: late fee applies after [date]

Hi [Client name],

A quick reminder that invoice #[number] for [amount] was due on [due date] and is still open.

Under our agreement, a late fee of [fee or rate] applies to balances unpaid after [date]. If you can pay before then, no fee will be added.

Payment link: [payment link]

Thanks,
[Your name]

Step 6: Apply the fee with an updated invoice

When the fee applies, send an updated invoice that adds the fee as its own line, shows how you calculated it, and keeps the original invoice number for reference.

Subject: Updated invoice #[number] with late fee

Hi [Client name],

Invoice #[number] is now [X] days past its due date of [due date]. As set out in our agreement dated [date], a late fee of [fee amount] has been added ([how it was calculated]).

The updated balance is [new total]. The revised invoice is attached, and you can pay here: [payment link]

If you have any questions about the amount, just reply and I'll walk you through it.

Thanks,
[Your name]

When to waive the fee

Waiving a fee can be a smart move with a good long-term client who is rarely late, or when the delay was partly your fault, such as an invoice sent to the wrong person. If you waive it, say so in writing, so the policy stays in place for next time.

Subject: Re: Invoice #[number]

Hi [Client name],

Thanks for sending payment for invoice #[number]. Since you're usually right on time, I've waived the late fee this once.

Just a heads-up that the late payment terms in our agreement will apply to future invoices as usual.

Thanks again,
[Your name]

Mistakes to avoid

• Adding a fee that was never in your agreement or invoice terms.
• Charging more than the law allows where you or your client are based.
• Compounding interest on top of interest unless your agreement clearly says so.
• Applying a fee without any warning to a client you want to keep.
• Letting fees replace reminders. A fee is a backstop, not a follow-up plan.

Reminders do most of the work

Late fees work best alongside steady reminders, because most clients pay once they're nudged at the right time. ChaseOwl sends polite reminders automatically on the due date and at 3, 7 and 14 days late, so fewer invoices ever reach the point where a fee applies. This guide is general information, not legal advice.

More guides

• Net 30 Payment Reminder Schedule: When to Follow Up (With Templates)
• What to Do When a Client Won't Pay: A Step-by-Step Plan for Freelancers
• Final Notice Before Collections: Templates and When to Send One

Free tools

• Late fee calculator: Enter the amount and due date to see days overdue and the late fee owed, as a flat fee or a monthly percentage.
• Payment reminder email generator: Write a friendly, firm or final reminder email for an unpaid invoice in seconds, ready to copy and send.
• Free invoice template: Fill in a clean invoice in your browser, then print it or save it as a PDF. No login needed.